Imaging device and focusing control method

Abstract

The present invention provides an imaging device and a focusing control method capable of enhancing accuracy of a focusing control regardless of subjects even when levels of detection signals of phase difference detection pixels are low. A phase difference AF processing unit ( 19 ) generates a defocus amount (Df 1 ) from a result of a correlation operation performed with respect to detection signals obtained by adding up detection signals of plural phase difference detection pixels ( 52 A, 52 B) in a pair line (PL 1 ) present in a selected AF area ( 53 ) and detection signals of phase difference detection pixels ( 52 A, 52 B) in pair lines (PL 2 , PL 3 ) present in a selected direction among plural directions which are crossing directions crossing an X direction with respect to each of the plural phase difference detection pixels ( 52 A, 52 B) in the pair line (PL 1 ). A system control unit ( 11 ) performs a focusing control based on the defocus amount (Df 1 ).

What is claimed is: 
     
       1. An imaging device comprising:
 an imaging element that includes a pair line in which a plurality of pairs of a first signal detection pixel that detects a signal corresponding to a beam that passes through a divided region among divided regions of a pupil region divided in a specific direction in an imaging optical system and a second signal detection pixel that detects a signal corresponding to a beam that passes through the other divided region is arranged in the specific direction, in which the plurality of pair lines is arranged in a direction orthogonal to the specific direction; and 
 at least one of processors configured to 
 generate a defocus amount from a result of a correlation operation performed with respect to a plurality of detection signals obtained by adding up detection signals of the plurality of first signal detection units in an arbitrary pair line present in an area where the plurality of pair lines is arranged and detection signals of the first signal detection pixels in a different pair line in the area, present in a crossing direction crossing the specific direction with respect to each of the plurality of respective first signal detection pixels, and a plurality of detection signals obtained by adding up detection signals of the second signal detection pixels that forms pairs in combination with each of the plurality of first signal detection pixels in the arbitrary pair line and detection signals of the second signal detection pixels in the different pair line in the area, present in the crossing direction with respect to the second signal detection pixels; 
 determine a direction where a reliability of the result of the correlation operation becomes a maximum among a plurality of directions as the crossing direction; and 
 perform a focusing control for the imaging optical system based on the generated defocus amount from the result of the correlation operation performed using the determined direction as the crossing direction. 
 
     
     
       2. The imaging device according to  claim 1 ,
 wherein the processor sets each of the plurality of directions as the crossing direction to perform the correlation operation, and determines the direction where the reliability becomes a maximum by comparing the results of the correlation operations with respect to the plurality of respective directions. 
 
     
     
       3. The imaging device according to  claim 1 ,
 wherein the processor determines a direction where contrast of a subject image formed in the area becomes a minimum as the direction where the reliability becomes a maximum. 
 
     
     
       4. The imaging device according to  claim 3 ,
 wherein the processor calculates the contrast by integrating differences between detection signals of adjacent signal detection pixels using the plurality of respective first signal detection pixels or the plurality of respective second signal detection pixels in the arbitrary pair line and the first signal detection pixels or the second signal detection pixels in the different pair line in the area, present in the plurality of respective directions with respect to the plurality of respective first signal detection pixels or the plurality of respective second signal detection pixels in the arbitrary pair line. 
 
     
     
       5. The imaging device according to  claim 1 ,
 wherein the processor determines a direction which is closest to a direction of gravity among the plurality of directions as the direction where the reliability becomes a maximum. 
 
     
     
       6. A focusing control method of the imaging device according to  claim 1  comprising:
 a defocus amount generation step of generating a defocus amount from a result of a correlation operation performed with respect to a plurality of detection signals obtained by adding up detection signals of the plurality of first signal detection pixels in an arbitrary pair line present in an area where the plurality of pair lines is arranged and detection signals of the plurality of first signal detection pixels in a different pair line in the area, present in a crossing direction crossing the specific direction with respect to the plurality of respective first signal detection pixels, and a plurality of detection signals obtained by adding up detection signals of the plurality of second signal detection pixels that forms pairs in combination with each of the plurality of first signal detection pixels in the arbitrary pair line and detection signals of the plurality of second signal detection pixels in the different pair line in the area, present in the crossing direction with respect to the second signal detection pixels, the detection signals being output from an imaging element that includes a pair line in which a plurality of pairs of a first signal detection pixel that detects a signal corresponding to a beam that passes through a divided region among divided regions of a pupil region divided in a specific direction in an imaging optical system and a second signal detection pixel that detects a signal corresponding to a beam that passes through the other divided region is arranged in the specific direction, in which the plurality of pair lines is arranged in a direction orthogonal to the specific direction; 
 a direction determination step of determining a direction where a reliability of the result of the correlation operation becomes a maximum among a plurality of directions as the crossing direction; and 
 a focusing control step of performing a focusing control for the imaging optical system based on the defocus amount generated in the defocus amount generation step from the result of the correlation operation performed using the direction determined in the direction determination step as the crossing direction.